1. Field of the Invention
The present invention relates generally to maintenance and repair of conduits, such as underground pipelines and ducts and, more particularly, to a device and a method for lining or relining such conduits.
2. Description of the Prior Art
It is common to use conduits buried in the ground for sewage, drainage systems, and the like. Although these underground systems are quite satisfactory for their purposes, it has been found that over a certain period of time, these conduit systems can deteriorate and become damaged.
Conventional methods of repairing underground conduits generally consist in applying a pre-mixed lining mixture on the inner wall of the damaged conduit by supplying at low pressure the pre-mixed lining mixture on a revolving disc so as to cause the lining mixture to be centrifuged against the inner wall of the conduit. The pre-mixed lining mixtures are typically made of mortar or epoxy. Such lining mixtures require relatively long drying period.
Although it is known to spray quick setting lining mixtures, such as polyurethane, on a surface to be rehabilitated, the use of such lining mixtures in conduits have been so far greatly limited due to the minimum distance required between the spray source and the surface to be rehabilitated and also because of the difficulty of uniformly applying the sprayed mixture to the inner circumferential walls of the conduits. Known polyurethane sprayers are typically in the form of spray guns manually operated and requiring a distance of about 24 inches between the spray source and the surface to be rehabilitated. The height of such spray guns typically varies between 10 to 12 inches. The dimensions of the guns and the minimum required application distances render the utilization of such guns quite hazardous and sometimes even impossible in conduits having an internal diameter of about 36 inches or less. Furthermore, the manual operation of the guns does not allow for a uniform application of the spray-applied liner.
There is thus a need for a novel method and a compact apparatus for applying a fast setting lining material to the inner walls of a wide variety of conduits.